Meanwhile, less competitive primary races ended early and with predictable results. Here’s a look at the congressional primary races in Nevada:

4th DISTRICT

Two-term Nevada Assemblyman Hardy, who hails from Mesquite, slid past Innis, a national spokesman for the Congress on Racial Equality.

“I think Niger did a good job. He put up a good campaign,” Hardy said after his victory. “But I’m proud that the voters of this state agree with me.”

Innis raised questions late Tuesday about how a virtually unknown candidate in the race, Mike Monroe, garnered a sizeable 23 percent of the vote. He said he planned to formally request an investigation by the secretary of state and wouldn’t concede the race until the question is resolved.

Innis and Hardy had raised nearly identical amounts of campaign money and had trumpeted their conservative credentials during four debates. Innis criticized his rival as someone willing to bend to Democrats, citing legislative votes to implement President Barack Obama’s health care law.

Hardy, meanwhile, criticized Innis for failing to vote for much of his adult life.

Hardy faces a tough contest against Horsford, the state’s first black member of Congress, who trounced a pair of little-known challengers, Mark Budetich Jr. and Sid Zeller, in his bid for the Democratic nomination. His district stretches from urban North Las Vegas to the rural northern towns of Yerington and Ely.

“After a year and a half on the job, I am under no illusion that making Washington work is easy,” Horsford said in a statement Tuesday after declaring victory. “But I am also not disillusioned. With hard work, we can make a difference in the lives of working Nevadans who need someone to stand by their side.”

3rd DISTRICT

Erin Bilbray beat a little-known primary opponent, Zachary “Mr. Z” Campbell, for the Democratic nomination in the In the 3rd Congressional District.

The competition for the district, which includes suburban Henderson and Summerlin, is expected to heat up quickly.

“I’m excited, and I’m ready to work hard,” Bilbray said after her victory. “I know this is a real battle that needs to be fought and won.”

Democrats hope they can leverage their 1 percentage-point registration advantage in the district to unseat Heck. But registered nonpartisan voters, who account for 19 percent of the electorate, will likely decide the race in November.

Heck leads in fundraising, with almost four times as much campaign cash as Bilbray, according to reports filed with the FEC.

Bilbray, the daughter of four-term former U.S. Rep. James Bilbray, founded Emerge Nevada, which trains female political candidates.

Heck, a doctor and member of the Army Reserves, serves on the House armed services, intelligence and education and workforce committees. In 2012, he defeated his Democratic opponent, John Oceguera, by 7 percentage points.

2nd DISTRICT

Incline Village attorney Kristen Spees emerged as the winner of a crowded field seeking the Democratic nomination in the 2nd Congressional District.

She will face incumbent Republican Mark Amodei, who faced no primary opponent and is expected to easily retain his seat in the general election.

The district, which covers the northern portion of the state and never has elected a Democrat, is 43 percent Republican, 33 percent Democratic and 17 percent registered nonpartisan.

Three other candidates with no political experience sought the Democratic nomination, including Reno physician Vance Alm, Gardnerville store clerk Brian Dempsey and Reno engineer Ed Lee.

1st DISTRICT

Dr. Annette Teijeiro defeated lawyer Jose Padilla in a competitive GOP primary. She faces an uphill battle in the 1st Congressional District, where Republicans are outnumbered 2-to-1 by Democrats, but sounded an optimistic note about her race against Rep. Dina Titus.

“All I ever wanted to do is see a representative of the people,” Teijeiro said. “Being bilingual, bicultural … I share a lot of experiences of people in this district.”

She had faced off with a fellow Hispanic candidate who also came from an immigrant family in a district that is 43 percent Latino.

“I’m disappointed by the results, but I’m happy about what I did,” Padilla said after his loss. “I knocked on a lot of doors. I talked to a lot of people. I had people who reached out to me - Hispanics who feel there aren’t a lot of options for them in either party.”

Titus scored an easy victory Tuesday against her lone Democratic primary challenger, Herbert Glenn Peters. The defeat adds to Peters’ losing record, which also included eight congressional race losses in in Nevada and California.

While she’s expected to sail to victory in November, “we never take any election for granted,” Titus said. “We’ll continue working hard for the district.”